Conventionally, a snap-fit system is employed for the fitting of a case and a valve assembly in this kind of air bypass valve device, as disclosed in Patent Document 1 and Patent Document 2. The fitting of the case and the valve assembly (assy) is not a matter which is directly relevant to an operating principle; however, if the fitting is not prepared, a spring, the case, and the valve assembly in which a holder, a diaphragm, and a valve are integrally assembled are put in an individual state as three parts until an installment thereof to a compressor housing of a turbo charger. For this reason, there is a problem such that the working efficiency for mounting the parts to the compressor housing is very bad.
In order to solve the above-described problem, a snap-fit unit is prepared for the valve assembly; when the valve assembly is fitted in and assembled to the case in a state where the spring is compressed and stored by a flange of the snap-fit unit, the three parts put in an individual state can be transported and handled as one part, to thereby enhance the working efficiency for mounting the parts to the compressor housing of the turbo charger.
However, a length of the snap-fit unit needs to be increased to obtain a sufficient flexure amount thereof depending on the material property (physical property) of parts to be used; as a result, it is difficult to decrease the total height of the air-bypass valve device, namely, to obtain a thinner one.
There is no problem when a flexible resin material such as PA66 can be employed for the snap-fit unit; however, in the case that the material is changed (the resin material is changed to PPS and so on) for the purpose of increasing the heat resistance, a structure with the same height could not be achieved due to the poor resistance to flexure. For this reason, the snap-fit unit needs to be elongated to obtain a sufficient flexure amount thereof; however, an elongated snap-fit unit interferes with a nipple as a pressure port that is prepared in the case, which poses a problem such that an operating stroke amount of a product is reduced.
In order to solve this problem, it can be considered to move the nipple in an upper direction; however, in order to move the nipple in the upper direction, the size of the case needs to be increased, which leads to an increase of the total height of the air bypass valve device, resulting in the degradation of the mountability thereof on vehicles.